In this article

Convert Exchange 2007 mailboxes to mail-enabled users

In this article

After you have completed a staged migration, convert the mailboxes to mail-enabled users so that the mailboxes can automatically connect to the cloud mailbox.

Why convert mailboxes to mail-enabled users?

If you've completed a staged Exchange migration to migrate your organization's Exchange 2007 on-premises mailboxes to Office 365 and you want to manage cloud-based users from your on-premises organization—using Active Directory—you should convert the on-premises mailboxes to mail-enabled users (MEUs). Why? Two things happen after a mailbox is migrated to the cloud in a staged Exchange migration:

A user has an on-premises mailbox and a cloud mailbox.

Mail sent to the user's on-premises mailbox is forwarded to their cloud mailbox. This happens because during the migration process, the TargetAddress property on the on-premises mailbox is populated with the remote routing address of the cloud mailbox. This means that users need to connect to their cloud mailboxes to access their e-mail.

This behavior results in two issues:

If a person uses Microsoft Outlook to open their mailbox, the Autodiscover service still tries to connect to the on-premises mailbox, and the user won't be able to connect to their cloud mailbox. If there are users that haven't been migrated to the cloud, you can't point your Autodiscover CNAME record to the cloud until all users are migrated.

If an organization decommissions Exchange after all on-premises mailboxes are migrated to the cloud, messaging-related user information on the cloud mailbox will be lost. The Microsoft Online Services Directory Synchronization tool (DirSync) removes data (such as proxy addresses) from the cloud mailbox object because the on-premises mailbox no longer exists and DirSync can't match it to the corresponding cloud mailbox.

The solution is to convert the on-premises mailbox to a mail-enabled user (MEU) in your on-premises organization after the user's mailbox has been migrated to the cloud. When you convert an on-premises mailbox to an MEU:

The proxy addresses from a cloud-based mailbox are copied to the new MEU; if you decommission Exchange, these proxy addresses are still retained in Active Directory.

The properties of the MEU enable DirSync to match the MEU with its corresponding cloud mailbox.

The Autodiscover service uses the MEU to connect Outlook to the cloud mailbox after the user creates a new Outlook profile.

PowerShell scripts to create MEUs

You can use the scripts below to collect information about the cloud-based mailboxes, and to convert the Exchange 2007 mailboxes to MEUs.

The following script collects information from your cloud mailboxes and saves it to a CSV file. Run this script first.